KVM-PR no longer works when compiled with new GCC compilers

[John Paul Adrian Glaubitz]

Hi Christian,

On Thu, 2026-04-23 at 18:50 +0200, Christian Zigotzky wrote:
> On 02/10/25 08:37, Christian Zigotzky wrote:
> > Hello,
> > 
> > KVM-PR (-enable-kvm) doesn't work anymore on our PA Semi Nemo boards 
> > [1] if we compiled it with new GCC compilers.
> > The VM can't boot. There aren't any messages on the serial console of 
> > QEMU.
> > 
> > It boots without KVM-PR.
> > 
> > Kernel config with new GCC compiler [2]:
> > 
> > - CONFIG_CC_VERSION_TEXT="powerpc64-suse-linux-gcc (SUSE Linux) 11.5.0"
> > - CONFIG_TARGET_CPU="power4"
> > - CONFIG_TUNE_CPU="-mtune=power10"
> > 
> > It works if I compile it with an old GCC compiler [3]:
> > 
> > - CONFIG_CC_VERSION_TEXT="powerpc-linux-gnu-gcc (Ubuntu 
> > 9.4.0-1ubuntu1~20.04.1) 9.4.0"
> > - CONFIG_TARGET_CPU="power4"
> > - CONFIG_TUNE_CPU="-mtune=power9"
> > 
> > Mtune changes to power9 automatically if I compiled it with an old GCC 
> > compiler. If I compile it with a new GCC compiler again it changes 
> > automatically to mtune=power10.
> > 
> > Is mtune the reason of the KVM-PR issue? I think the issue is the new 
> > GCC. [4]
> > 
> > Could you please check whether KVM-PR is compatible with new versions 
> > of GCC compilers?
> > 
> > Thanks in advance,
> > 
> > Christian
> > 
> > 
> > 
> > [1] https://en.wikipedia.org/wiki/AmigaOne_X1000
> > 
> > [2] 
> > https://github.com/chzigotzky/kernels/blob/45186997e6f347fd092f9ab629d62d6041426227/configs/x1000_defconfig
> > 
> > [3] 
> > https://github.com/chzigotzky/kernels/blob/bc7a3e27b3fcdee52a8135435f02cf807a43872a/configs/x1000_defconfig
> > 
> > [4] KVM-PR no longer works on an X1000 if the kernel has been compiled 
> > with a new GCC: 
> > https://forum.hyperion-entertainment.com/viewtopic.php?p=57146#p57146
> > 
> Error messages (kvm-pr compiled with powerpc64-linux-gnu-gcc 14.1.1 
> 20240507 Red Hat Cross 14.1.1-1, GNU ld version 2.41-2.el10_0):
> 
> [  800.274759] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
> [  800.274767] kvmppc_exit_pr_progint: emulation at 100 failed (00000000)

I don't think "mtune=power9" or "mtune=power10" will work. Did you try "mtune=power4"?

Adrian

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